Accelerating metronome



United States Patent Office Patented Mar. 3, 1970 3,498,169 ACCELERATING METRONOME William J. Gollan, P.0. Box 686, Redlands, Calif. 92373 Filed Sept. 27, 1968, Ser. No. 763,219 Int. Cl. G04b 21/00 US. Cl. 84484 6 Claims ABSTRACT OF THE DISCLOSURE An electronic metronome in which the beat may be preset to any desired starting frequency, and in which the frequency slowly and imperceptibly accelerates over a period of time to a faster rate, thereby gradually leading the student to a faster rate of playing without his being aware of the speed-up. Timing is by an R-C series circuit, in which the time constant is varied by means of an adjustable potentiometer. A motor having a drive shaft turning at 1 revolution per hour is connected to the potentiometer, so as to advance the potentiometer slowly while the unit is in operation.

BACKGROUND OF THE INVENTION Electronic metronome for pacing students learning to play musical instruments have been known for many years, an example of which may be seen in US. Patent No. 2,522,492 to Andersen. In the patented electronic metronome, timing of the beat frequency is accomplished by means of an R-C series circuit, the time constant of which is adjusted by means of an adjustable potentiometer. The movable contact of the said adjustable potentiometer is connected to a shaft having an adjustment knob on one end thereof. There is a pointer, or index mark, on the knob, which cooperates with a graduated scale marked in beats per minute, and the pointer is manually set to the desired beat frequency. The metronome then operates at the selected frequency rate until the knob is again manually turned to another frequency.

Heretofore, the student practicing a new lesson would start at a fairly slow rate, and when he felt competent to play at a faster rate, would stop playing and set the metronome to operate at the faster rate. He would continue this step-by-step increase in his playing rate until he reached the desired speed, or until he found that the speed was beyond his capability. One disadvantage of this step-by-step increase in the frequency rate is that the student is fully aware of each increase in speed, and therefore becomes apprehensive of his ability to play at the faster rate. As a result, he tends to become nervous and tense, and finds himself making mistakes that he would not make if he were more relaxed and at ease. Another disadvantage is that each upward step represents a fairly substantial increase in speed. As the student approaches the upper limit of his playing ability, even small additional increments in speed call for the utmost effort on his part, and a too-abrupt increase may exceed the limit of his ability without actually bringing him up to that limit. It is desirable that the students playing speed be increased as gradually as possible, and that he continue to play for as long as possible at the fastest speed of which he is capablepreferably without interruption.

SUMMARY OF THE INVENTION The present invention relates to accelerating metronomes, and its primary object is to provide a metronome the speed really is, until he reaches a predetermined maximum speed, or reaches the upper limit of his playing ability. In either case, the student is slowly and gradually paced up to his maximum speed, without interruption, and without the apprehension and tension which oftentimes results when a student manually sets a metronome to operate at a speed which he believes is beyond his capability.

The above object is achieved by providing a metronome in which the beat frequency is adjustable by means of a movable adjustment control, together with driving means for automatically advancing said control from a preset starting speed to a much faster speed over an extended period of time. More specifically, the invention has to do with an electronic metronome having an R-C series circuit for the timer, the timer constant of which is varied by means of an adjustable potentiometer. The adjustable contact of the potentiometer is driven by means of a motor having a drive shaft that turns at the rate of one revolution per hour, and in the course of a half-hour practice session, the beat frequency could, for example, be advanced from as low as 40 beats per minute to as high as 200 or more beats per minute. However, in most cases the student will want to increase his speed from perhaps 60 beats per minute to 120, and therefore another object of the invention is to provide a metronome of the class described, in which the acceleration of the beat frequency can be stopped at any desired point, so that the unit thereafter continues to operate at the preselected maximum frequency. In the case of the electronic metronome, this is accomplished by providing an adjustable limit stop, which stops the potentiometer at the selected point.

The foregoing and other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment thereof, which is illustrated in the drawings. 1

DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of an electronic metronome embodying the principles of my invention;

FIGURE 2 is an enlarged sectional view through the same, taken at 2-2 in FIGURE 1; and

FIGURE 3 is a circuit diagram, showing the timer circuit and the apparatus for advancing the potentiometer to increase the beat frequency rate.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, an accelerating metronome embodying the principles of the invention is designated in its entirety by the reference numeral 10, and comprises a housing 12 of molded plastic or the like, which is mounted on a bottom plate 14. A calibrated scale 16 graduated in number of beats per minute, is inscribed on the front of the housing 12, and cooperating with this scale is a pointer 18 formed integrally with an adjustment knob 20-. In the upper left-hand corner of the front side of the housing is an on-oif switch 22, and in the upper righthand corner is a neon lamp 24, which flashes with each beat of the metronome. Projecting from the back side of the housing is the knurled head 25 of a volume adjustment screw 26 (FIG. 2) for increasing or decreasing the loudness of the audible sound, or beat, produced by the metronome.

Mounted on the bottom plate 14 within the housing 12 is an inverted, channel-shaped base 28. Attached to the bottom side of the base is a box 30 containing the electronic circuit shown in FIG. 3. Part of the said circuit includes an adjustable potentiometer 32 which is mounted on the front wall of the base 28, and projecting forwardly from said potentiometer is a rotatable adjustment shaft 34, which extends through a hole in the front of the housing. The adjustment knob and pointer 18 are mounted on the front end of shaft 34. Mounted on the base above the potentiometer 32 is a motor 36 having an integral speed-reduction gear box 38, the drive shaft 40 of which turns at the rate of approximately 1 revolutron per hour. A pulley 42 is mounted on drive shaft 40, and directly below it i a second pulley 44 mounted on shaft 34. Pulleys 42, 44 are connected together in driving relationship by a belt 46. Mounted on the top of base 28 behind motor 36 is a grid-controlled, gasfilled thyratron tube 48, forming part of the circuit shown in FIG. 3.

The sound pulses, or beats, are produced by a device similar to that shown in Patent No. 2,522,492, consisting of a steel plate 50 rising vertically from the base 28 near the rear edge thereof, and having a sounding board 52 mounted thereon about midway between its ends. The sounding board 52 is struck at regularly spaced intervals by an electromagnet 54, which is mounted on a resilient strip 56, also of steel. Strip 56 extends generally parallel to plate 50, and is angularly bent near its bottom end toward the plate to which it is secured. The other end of the strip is engaged by the inner end of adjusting screw 26, which is screwed through a threaded nut 58 mounted on the upper end of plate 50. As the electromagnet 54 is energized, it is drawn toward the plate 50, bowing the strip 56, and striking against the sounding board 52. When the screw 26 is turned clockwise through the nut 58, the top end of the strip 56 is pushed further away from the plate 50, thereby increasing the distance separating the electromagnet 54 from the sounding board 52. This has the effect of decreasing the strength of magnetic attraction between the magnet 54 and plate 50, thereby decreasing the volume of the tick, or beat. To increase the volume, screw 26 is turned in the counterclockwise direction to bring the electromagnet 54. closer to the sounding board 52.

The circuit arrangement for producing the electrical pulses which energize the electromagnet 54 is shown in FIG. 3. Essentially, the electronic timer consists of an R-C series circuit 60 and the grid-controlled rectifier 48, which is a gas-filled thyratron. The thyratron includes a anode 70, cathode 62, control grid 64, auxiliary control grid 66, which is externally connected with the cathode 62 and interposed between the pontrol grid 64' and anode 70, and filament 68. Electrical current for heating the filament 68 is supplied by a transformer 72.

Power for the unit is supplied through a power supply 74, which may be domestic 110-volt A.C. current. The cathode 62 of the thyratron is connected in series with the electromagnet 54 and basic timing circuit 60, to the opposite side of the power supply line. The R-C series circuit 60 consists essentially of a first capacitor 76 and first resistor 78 connected together in parallel, together with a second capacitor .80 and second resistor 82, also connected together in parallel. The resistance-capacitance combination 76, 78 is connected through a resistor 84 and neon lamp 24 to one side of the electromagnet 54. The second resistor 82 is connected to a trimmer resistor 86, and the resistance-capacitance combination 80', 82, 86 is connected to the top end of the electromagnet 54, on the right-hand side of neon lamp 24. The movable tap 88 of potentiometer 32 is connected through a currentlimiting resistor 90 to the control grid 64 of the thyratron, and one end of the potentiometer element 92 is connected to one side of the line 74, while the other end thereof is connected through a resistor 94 to the other side of the line.

When switch 22 is closed, motor 36 is started running, and this starts output shaft 40 to turning at one revolution per hour. At the same time, the thyratron filament 68 is heated to operating temperature, and when a positive voltage is applied to the anode 70 on each half cycle of the A.C. potential, the thyratron 48 conducts,

4 and a pulse of current flows from the cathode 62, charging capacitors 76 and and energizing electromagnets 54. This pulse of current flowing through the electromagnet 54 causes the latter to strike against the sounding board 52, emitting an audible tick, or beat. As the current pulse charges capactor 80, the voltage thereon causes the neon lamp 24 to glow for an instant while current through it charges capacitor 76. When the capacitor 76 charges sufficiently, the voltage across lamp 24 becomes so low that it will not maintain a discharge and is thus extinguished.

As the cathode-anode voltage of the thyratron 48 reduces owing to charging of the capacitors 76 and 80, and the alternation of the A.C. voltage is applied to the plate 70, a point is reached where the thyratron is extinguished. The capacitors 76, 80 discharge through the resistances 78 and 82, 86, until the voltage between the thyratron-cathode and anode again is sufiicient so that for a positive cycle of voltage the thyratron again fires, and the cycle is repeated.

Current flows through the lamp 24 for only a small part of the time interval during which condenser 76 is discharging. Inasmuch as the discharge current through the lamp 24 occupies a small fraction of this total discharge current, variations of lamp characteristics have minimum effect on the timing, and pulse repetition rate of the circuit. Between pulses, while the lamp 24 is extinguished, the capacitor 80 discharges through resistors 82, 86. It is desirable that the time constant 80-82-86 be approximately the same as that of 78-80.

Adjustment of the voltage applied to the thyratron grid 64 by means of the adjustable potentiometer 32 determines the cathode-anode voltage required for refiring the thyratron, and determines the time delay between successive pulses. Thus, the circuit provides means for creating both audible and visual signals at timed intervals. Inasmuch as the pulse occurs when the anode 70 is positive, the device tends to repeat its pulsing in an integral number of half-cycles of the A.C. waves supplying the system. The basic timing of the system is controlled by the resistance-capacitance combination 76, 78 and 80, 82, and the setting of the tap 88 on potentiometer 32.

In practice, the potentiometer 32 has a calibrated scale substantially like that shown in FIG. 1. While a wide range of frequencies is obtainable, for musical work the range between 40 and 208 beats-per-minute is preferred. This is obtained by proper choice of the time constant 7678, 80-82, and of resistors 94 and 92. Resistor 94 can be so chosen that a desired range is covered by the maximum excursion of the tap on resistance 92.

The values of the several components in the circuit are rather critical for proper operation of the metronome, and the following values have been found to give good results in the circuit shown.

Resistors 78--l megohm 82--330K ohms 84-6800 ohms 86Mode1 LS9522 Trimpot, mfg. by Bourns, Inc.

90--l megohm 944700 ohms Potentiometer 32-20,000 ohms Capacitors: 76-O.47 microfarad 80-O.47 inicrofarad Thyratron 48-RCA2050, RCA2051, RCA2D21 or RCA2A4G If it is desired to stop the potentiometer tap 88 at any given point, thereby holding the metronome at a constant frequency rate, this can be done by means of an adjustable limit stop 96, in the form of a pin which can be inserted into any one of a series of holes 98 arranged in a semi-circle concentric with the axis 'of rotation of the dial 20. When the pin 96 is inserted into one of the holes 98, the pointer 18 eventually abuts apinst the pin and is stopped thereby from further turning. When this occurs, the belt 46 slips on one or both of the pulleys 42, 44 andthe potentiometer tap 88 remains fixed in the desired position on the resistance 92, thereby maintaining the metronome at a constant frequency. In this way, the student can work up to any predetermined frequency rate, and then hold that rate for any desired period of time while he continues to play at that rate.

During a normal half-hour practice session, the student might begin practicing a new lesson, starting at 70 beats per minute, with the intention of trying to reach 150 beats per minute .by the end of the session. He would then turn the knob 20 to set the pointer 18 on the scale graduation marked 70*. If he wanted to keep the metronome from going beyond 150 beats per minute, he would set the limit stop pin 96 in the hole 98 corresponding to 150 on the scale; otherwise, he might leave the pin 96 out and let the unit go as high as it will during the practice session, or until it exceeds his capability, at which point he might reset the pointer to a slower rate. With the timing range thus set, the student would flip the switch 22 to the On position and start playing.

The unit would start ticking at the 70 beat-per-minute rate, while the student concentrates on mastering the ploying technique of the new lesson. As the unit goes on ticking, the motor .36, 38 slowly and almost imperceptibly turns the potentiometer shaft 34, advancing the tap 88 along the element 92. This causes the unit to accelerate its beat frequency at such a slow rate that the student is totally unaware of the speed-up. In a halfhours time, the shaft 34 could make a 180 turn, advancing the tap 88 all the way from one end of the potentiometer element 92 to the other. However, if the pin 96 has been inserted in one of the holes 98, the pointer 18 will be stopped by the pin at that point, and the unit will then go on ticking at the same frequency rate until it is turned off. If the pin has not been inserted in one of the holes, the student will oftentimes find that he has reached an appreciably higher playing speed than he though he was capable of, before finally exceeding his limit.

I claim:

1. In a metronome having means for producing repetitive audible sounds at a controlled frequency rate,

and adjustable control means for varying the frequency rate, the improvement comprising:

means for slowly and almost imperceptibly advancing said adjustable control means in the direction to increase the frequency rate from a preselected minimum rate to a higher terminal rate.

2. The invention as set forth in claim 1, wherein said control means for varying the frequency rate of said sound-producing means comprises an adjustable potentiometer having a rotatable adjustment shaft, and said means for advancing said control means comprises an electric motor having a drive shaft connected to said adjustment shaft, said drive shaft turning at a very slow rate of speed, of the order of 1 revolution per hour.

3. The invention as set forth in claim 2, wherein said repetitive sound producing means includes an R-C series circuit, the frequency rate of which is varied by said adjustable potentiometer.

4. The invention as set forth in claim 2, additionally including means for stopping the advancement of said rotatable adjustment shaft of said potentiometer at any predetermined point.

5. The invention as set forth in claim 3, wherein said rotatable potentiometer shaft has a manually controllable knob mounted thereon to permit adjusting said potentiometer to any desired setting, said driving connection between said motor and said potentiometer shaft permitting slippage to allow for said manual adjustment of said knob.

6. The invention as set forth in claim 3, wherein said electric motor drive shaft and said rotatable potentiometer shaft have pulleys mounted thereon, and said pulleys are connected together by a drive belt.

References Cited UNITED STATES PATENTS 2,522,492 9/1950 Andersen 58-130 

